Last month’s explosive news from the safe, reliable nuclear deterrence folks is that at least four barrels of military radioactive waste either burst or exploded somewhere inside the Idaho National Laboratory (INL), near Idaho Falls, April 11. INL officials said the “ruptured” barrels reportedly contained a sludge of fluids and solvents sent from the long-shuttered Rocky Flats plutonium weapons machining site near Denver. The officials did not describe which radioactive materials were in the sludge.

The accident was reported by ABC News, the Associated Press, the Seattle Times, the Japan Times, Industrial Equipment News, and Fox Radio among others. Laboratory spokespersons said a 55-gallon drum, or two, holding radioactive sludge “ruptured.” Energy Department (DOE) spokesperson Danielle Miller wrote April 12 that, “Later, there were indications that a third drum may have been involved.” On April 25 Erik Simpson, a spokesman for DOE contractor Fluor Idaho, told the AP that four barrels had burst. Simpson said the “ruptures” (i.e. explosions) were heard outside the building where they took place.

The DOE’s Miller called the prompt deconstruction of the rad waste barrel(s) an “exothermal event” — a pseudonym for “bomb” that means “a chemical reaction accompanied by a burst of heat.” The phrase harks back to the officially described “gaseous ignition event” involving hydrogen gas in a loaded high-level rad waste cask at Wisconsin’s Point Beach reactor site in May 1996. The cask contained 14 tons of highly radioactive used reactor fuel, and the explosion (a word avoided only by agency public relations linguistic gymnastics) blew the high-level waste cask’s 4,000-pound lid right off.

One theory about the cause of the accident is that “radioactive decay made the barrel[s] heat up and ignite particles of uranium,” the AP reported. Unfortunately for the first responders, “When the firefighters left the building emergency workers detected a small amount of radioactive material on their skin,” the AP reported April 12.